MM54HCT688 MM74HCT688 8-Bit Magnitude Comparator (Equality Detector)
February 1988
MM54HCT688 MM74HCT688
8-Bit Magnitude Comparator (Equality Detector)
General Description
This equality detector utilizes advanced silicon-gate CMOS
technology to compare bit for bit two 8-bit words and indi-
cate whether or not they are equal The P
e
Q output indi-
cates equality when it is low A single active low enable is
provided to facilitate cascading of several packages and en-
able comparison of words greater than 8 bits
This device is useful in memory block decoding applica-
tions where memory block enable signals must be generat-
ed from computer address information
The comparator combines the low power consumption of
CMOS but inputs are compatible with TTL logic levels and
the output can drive 10 low power Schottky equivalent
loads
MM54HCT MM74HCT devices are intended to interface be-
tween TTL and NMOS components and standard CMOS
devices These parts are also plug in replacements for LS-
TTL devices and can be used to reduce power consumption
in existing designs
All inputs are protected from damage due to static dis-
charge by diodes to V
CC
and ground
Features
Y
Y
Y
Y
Y
TTL input compatible
Typical propagation delay 20 ns
Low quiescent current 80
mA
maximum (74HCT Series)
Large output current 4 mA
Same as HCT521
Logic Diagrams
TL F 5371 鈥?2
C
1995 National Semiconductor Corporation
TL F 5371
RRD-B30M105 Printed in U S A
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